1. Field of the Invention
The present invention relates to a preset tuner control system for automatically controlling the tuning frequency of a klystron vacuum tube in a radio transmitter system, and more particularly, to a circuit for compensating for the backlash of the tuner's tuning mechanism.
2. Description of Prior Art
A kylstron power amplifier is employed in a transmitter system for use in satellite communication or satellite tracking control. A cavity tuning control of the amplifier is required by any change in the transmitting frequency of the klystron and should desirably be accomplished automatically and accurately. Unless this cavity tuning control is properly accomplished, the amplitude vs. frequency characteristics cannot be faithfully reproduced.
Since gears, chains and drive screws are used in the tuning mechanism of a klystron cavity, the presence of minute gaps between these components may cause a backlash. A preset tuner of an analog type servo mechanism controls the tuning shaft of the klystron with a D.C. motor. When the motor turns in the clockwise or counter-clockwise direction, as desired, there is a deviation corresponding to the backlash between the driving of the tuning shaft of the klystron cavity in the clockwise direction and in the counter-clockwise direction. As a result of this backlash, there is a failure to achieve a proper adjustment of this tuning shaft.